1. Field of the Invention
The present invention concerns a process for preparing (polyfluoroalkyl)polyfluoroarenes.
2. Background of the Invention
(Polyfluoroalkyl)polyfluoroarenes are useful as intermediates for high temperature solvents, synthetic oxygen carriers, solder masks and other chemical syntheses. Typically, these compounds are prepared by exhaustive fluorination of the corresponding hydrocarbons by either electrochemical techniques or reactions with CoF.sub.3. One problem associated with these techniques or reactions is the presence of residual hydrogen in the resulting compositions. It has been found that residual hydrogen adversely affects the stability of the compounds in critical applications such as high temperature solvents and synthetic oxygen carriers. Improved processes for preparing these compounds are of interest to the chemical industry.
Japanese Patent JP-026876 discloses the preparation of perfluoroalkyl benzene derivatives from benzene derivatives, metallic copper, and perfluoroalkyl iodide. The benzene derivatives have the formula C.sub.6 H.sub.4 R.sup.1 R.sup.2 wherein R.sup.1 and R.sup.2 are H, halogen, alkyl, substituted alkyl, amino, amido, carboxyl, alkoxycarbonyl, hydroxyl, alkoxy, substituted alkoxy, aryloxy, acyl, acyloxy, aryl or cyano. The products have the formula C.sub.6 H.sub.3 R.sup.1 R.sup.2 R.sub.f wherein R.sup.1 and R.sup.2 are as defined above and R.sub.f is a perfluoroalkyl group containing from 1 to 7 carbon atoms.
McLoughlin et al., Tetrahedron, 25: 5921 (1961) discloses that iodofluoroalkanes and iodoaromatic compounds react with copper in polar aprotic solvents to give (fluoroalkyl) aromatic compounds. The reference discloses that the iodofluoroalkanes and iodoaromatic compounds can bear a wide variety of substituents (carboxyl, nitro, amino, hydroxyl, etc.). In one reaction, C.sub.6 F.sub.5 C.sub.7 F.sub.15 is prepared by reacting C.sub.7 F.sub.15 I, C.sub.6 F.sub.5 Br and Cu.degree. at 120.degree. C. In another reaction, C.sub.6 F.sub.5 (CF.sub.2).sub.3 C.sub.6 F.sub.5 is prepared by reacting C.sub.6 F.sub.5 Br, I(CF.sub.2).sub.2 I and Cu.degree. at 120.degree. C. These reactions were conducted in the presence of polar aprotic solvents.
Pass, J. Chem. Soc., 824 (1965) discloses dehydrochlorination reactions involving trifluoromethane. In one reaction, C.sub.6 F.sub.5 CF.sub.3 is prepared by reacting C.sub.6 F.sub.5 Cl with CF.sub.3 H at 700.degree. for 10 seconds in a nickel tube.